Heat Definition and 1000 Threads

Homework Statement Find the mass of water in this container when given a data plot of temperature (C) and Heat Added (kJ) I have NO idea where to even start with this.

A bar of iron is 0.5m long, 0.2m wide and 0.1m high (which means its volume is 1.0 × 10−2m3 and its surface area is 3.4 × 10−1m2 ). Iron has a density of 7900 kg m3 , a heat capacity of 400 J kg◦C , and a coefficient of linear expansion of 1.2 × 10−5 . The bar of iron is initially at 600K...

Homework Statement 1. The common form of the heat-diffusion equation governing the temperature distribution $$\rho C_p \frac{\partial T}{\partial t}=k\nabla^2T$$ Is this equation valid in any inertial frame of reference? (i.e. does it have the property of Galilean invariance?) If not, can it...

Homework Statement A 0.035 kg ice cube at its melting point is dropped into an insulated container of liquid nitrogen. How much nitrogen evaporates if it is at its boiling point of -196 C? Nitrogen has heat of vaporization of 200000 J/kg Ice's specific heat is 2100 J/kg*C Homework Equations...

Say you have an object with a negative heat capacity. This means that the object increases in temperature as it radiates energy and decreases in temperature as it absorbs energy. I don't understand why this object cannot be in thermal equilbrium with a reservoir. Any help would be greatly...

Sooooo... I have a Far infrared (FIR) sauna. It has large flat 'carbon' panel heaters. They get warm to the touch and won't burn you if you touch them. My non contact infrared thermometer zapper says that they get to about 70 degrees C. They are meant to be producing lots of FIR. A regular...

Homework Statement http://i.imgur.com/swYr8aw.jpg Homework Equations delta L=LalphadeltaT The Attempt at a Solution sorry for s**ty handwriting look at #8[/B] http://i.imgur.com/59Ew8vJ.jpg edit:click the links please. The forum software cropped the quality of the photo.

Homework Statement Find the steady state (equilibrium) solution for the following boundary value problem: ∂u/∂t = (1/2)∂2u/∂x2 Boundary condition: u(0,t) = 0 and u(1,t) = -1 Initial condition: u(x,0) = 0 Homework Equations u(x,t) = Φ(x)G(t) The Attempt at a Solution I have found the solution...

Homework Statement A satellite to reflect radar is a 3.5-m-diameter, 2.0-mm-thick spherical copper shell. While orbiting the earth, the satellite absorbs sunlight and is warmed to 50 °C. When it passes into the Earth's shadow, the satellite radiates energy to deep space. You can assume a...

How to calculate cooling time for a aluminum block in a steel crate placed in a room...both at 90°c ...how much time aluminum block will tak take to cool down to 25°c?

I want to pursue EE, but there are still some subjects in ME that I enjoy. Do heat transfer topics ever come up in EE? I would imagine cooling circuit board requires lots of knowledge of heat transfer/thermodynamics. I studied Haberman's PDEs as part of my chemistry undergrad and all it talked...

Homework Statement q = -kdp/dx Homework Equations q = heat flow k = constant p = thermal energy density The Attempt at a Solution This equation says that when heat flows from hot to cold the thermal energy density increases but why? I thought heat meant a higher thermal energy density and hot...

Normally, I prefer to do my own research, but I'm drawing a blank on this one. Any help would be appreciated. My understanding is that statistical mechanics accounts for all of the heat energy in a gas by the kinetic energy of the molecules. I also understand that atomic orbitals have different...

Hi all, I am currently considering a heat transfer problem. In this problem a rectangular vessel made of stainless steel is heated by a surrounding jacket with hot combustion flue gases flowing through it. This means that the heating of the rectangular vessel is achieved primarily through...

This seems basic, but I'm stuck. Look at the attached picture. I'm trying to find the temperature on the outer surface of the insulation. Is it not possible because I do not know the rate of heat transfer? How do pipe designers know the required thickness of insulation needed to reduce to a...

My friend and I were planning on possibly developing our own tobacco vaporizer, but we lack the electrical engineering knowledge. We know they are simple devices with few parts, (a battery usually being the largest one) and we just were not sure how exactly the electrical energy was transferred...

Homework Statement An ice cube of mass 0.01.kg at a temperature of 0 degrees Celsius is dropped into a cup containing 0.10kg of water at a temperature of 15 degrees Celsius. What is the max estimated change in temperature of the contents of the cup? SHC of water = 4200J per kg per kelvin...

A brilliant person once said “First get your facts strait, then proceed to distort them at will” or something like that. My question, is what would happen if say… a sun of relative density to our own, but only the size of a golf ball, just appeared in say… downtown LA, and sustained at that...

Why we use enthalpy(h) instead of internal energy(u) when we consider latent heat?

Homework Statement have you ever encountered this equation? it is the energy differential equation through a rectangular tube Homework Equations uρ(∂i/∂x)+vρ(∂i/∂y)+wρ(∂i/∂x)-[∂/∂x(k∂t/∂x)+∂/∂y(k∂t/∂y)+∂/∂z(k∂t/∂x)]=0 heat transfer coeff is k The Attempt at a Solution have you any idea how to...

Homework Statement Homework Equations PV = nRT \\ W = - \int_{V_i}^{V_f} P dV \Delta E_{int} = Q + W The Attempt at a Solution a)[/B] Since this is a cyclic process, the change in internal energy of the system is 0. \Delta E_{int} = 0 The process causes some ice to melt, meaning heat...

Homework Statement Homework Equations P = k A \frac{dT}{dx} The Attempt at a Solution a) Assuming steady state transfer, energy transfers through rods at the same rate everywhere. Letting T be the temperature at the point of welding. P_1 = k_1 A \frac{T_h-T}{L} \\ P_2 = k_2 A \frac{T -...

Homework Statement Liquid ammonia is heated as it flows at a mean velocity of 2 m s–1 through a circular pipe. The pipe, which has an internal diameter of 75 mm, is at a uniform temperature of 27°C, and the ammonia at a section 1.2 m from the inlet to the pipe has a temperature of –23°C. Use...

Hello everyone, I'm having problems understanding how to calculate heat load. Does anyone know what formula should i use? I tried to calculate energy needed to cool the gases to 20 F but i need specific heat witch i don't know how to calculate. Info in the picture. Thank you for your time :)

I am interested in whether it might be possible to select a more efficient heat expansion media for nuclear power plants than water, which has a very specific heat and a very high heat of vaporization. The high value of the specific heat and the heat of vaporization of water requires much...

Hello. How do I solve this equation without killing the k(y) term: I managed to derive an analytical solution for this one. I intend to run the numerical solution via Runge-Kutta but I can't stop myself from killing the k(y) term. I'm starting to think I'm doing something wrong... It goes...

Homework Statement I have some doubts about the method constructing chemical reaction process of quantum mechanics in the referencehttp://www.southampton.ac.uk/assets/centresresearch/documents/compchem/DFT_L2.pdf, for the example of ##H_2O## molecular dissociation to ##H^+## and ##OH^-## ions...

Hello! I encountered in a problem the terms heat capacity at constant volume and density (##n##) and heat capacity at constant chemical potential (##\mu##) and volume and I need to prove a relation between them. What is their definition? I thought that for the first one it would be...

I was thinking about fire last night and a question came to mind. Probably easy, but I'm not sure of the answer. Is heat the cause or effect of atoms vibrating? For heat to be hot, the atoms must be vibrating fast,but at the same time for atoms to vibrating fast they must be hot. I know I'm...

Homework Statement Homework Equations The Attempt at a Solution This is a solved question. The answer is given above. I can't understand why h1=h2. [/B]

I'm trying to build a fanless computer case for a small electronic device. I'm trying to figure out what type of heat-sink material I should use. I have a solid copper rod about 3cm in length with a radius of .05cm. I've determined and calculated the density, specific heat, thermal...

Hello, I can't seem to get the great data when I am running my heat sink model through ANSYS NLT. I feel like I am overlooking something. Is anyone experienced and has some guidance. It is a simple convection problem with a certain amount of watts running through a cooper pipe into a copper heat...

Homework Statement An Aluminium rod has a diameter of 40mm. and is 750mm long. If the temperature difference between the ends of the rod is 100C . Take the thermal conductivity of Aluminium to be 235 Wm-1K-1 Homework Equations k * A * ΔT / L The Attempt at a Solution 235 * 0.097 m * 100 /...

Dear all: I am studying the finite difference method for black scholes equation(heat equation form), and my Prof. asked me to use the Crank Nicolson and Compact Scheme to do it. But I cannot reach second order for the space, i.e., x . The error only reach 1st order and sometimes not stable, it...

I'm trying to design a double pipe heat exchanger for two different water lines. One line is chilled water of approximately 7degC and the other is chilled water return from an air handling unit, of around 12degC. I want to design this heat exchange for a capacity of approximately 22kW. The part...

Homework Statement WE have a thermally insulated metallic bar (from enviroment/surroundings) . It has a temperature of 0 ºC. At t=0 two thermal sources are applied at either end, the first being -10 ºC and the second being 10 ºC. Find the equation for the temperature along the bar T(x,t), in...

Homework Statement I am trying to calculate the efficiency of this heat engine that has two step. an adiabatic compression, followed by a linear expansion back to the original point. I keep getting an efficiency of 1, which I know can't be right... Homework Equations ##e = \frac{W}{Q_H}## The...

Homework Statement A Carnot heat engine takes 95 cycles to lift a 10 kg. mass a height of 11 m . The engine exhausts 14 J of heat per cycle to a cold reservoir at 0∘C. What is the temperature of the hot reservoir? Homework Equations η=1-(Tc/Th)=W/Qh The Attempt at a Solution I've tried...

Is the answer in my physics book wrong or did I miss something? Homework Statement A vessel whose walls are thermally insulated contains 2.40 kg of water and 0.450 kg of ice, all at 0.0°C. The outlet of a tube leading from a boiler in which water is boiling at atmospheric pressure is inserted...

Homework Statement I am given that a Chemical Company wants to implement a cascading refrideration cycle to provide 1 MM Btu/hr of cooling. We are given the three compounds we are using. Evaporator Temperature (F) Compresspr Out Pressure(psia) Cycle 1...

Homework Statement 5 kg of water at 60 degrees are put in contact with 1 kg of ice at 0 degrees and are thermally isolated from everything else. The latent heat of ice is 3.3x105 J/kg. What is the change of entropy of the universe when 100J of energy are transferred from the water to the ice...

Hello Physics Forums! My problem is as follows. I have a device that produces heat via Nichrome coils. I want to heat another small piece of metal (in this case stainless steel) with those Nichrome coils. I need to reach 175 degrees C, and so far I haven't found a readily available thermal...

Homework Statement Hello, I have a task to make a heat balance of the evaporator. To do this, I was told to carry a few smaller energy balances in different parts of the evaporator. One of the things I had to calculate was the heat generated during steam compression. -steam is entering...

Homework Statement Its been assumed that the surfaces TL and TR of the same constant temperature. Homework Equations Tmax = TL/R + (qdoto*L2)/(8*k) q = ΔT/R Rconvection = 1/hA The Attempt at a Solution The problem I am having with this question is conceptualising which dimensions to use...

I have been researching the Rankine cycle. I know that it consists of two adiabatic and two isobaric processes. However, I'm not entirely sure why we ignore the work done during the isobaric processes (this seems to be the case in the analysis I'm looking at). Is that because the work done there...

Can someone tell me if my logic is correct here. I am trying to figure out how the cross sectional area to make the heat transfer from one object be the maximum amount of heat transfer with the minimal amount of area... I know the thermal transfer coefficient is watts per (meter*kelvin). I find...

How we change the units of Heat capacity equation to British engineering system Cp=2. 657*10^4 +42. 37T - 1. 425*10^-2T^2

Homework Statement I was looking for some examples where gravitational potential energy is converted to heat energy. Are there many such examples of this conversion? I could only come up with one such example and even that could be an incorrect example. Homework Equations PEg = mgh The...

Hi. To prove that the Stirling cycle has Carnot efficiency, one needs to neglect the isochoric heat transfers. Sure they have the same absolute value (but different signs), but it's still heat energy lost to the cold reservoir during the isothermic compression.

Just a basic question. It's as the title says, If I'd want to determine the latent of oils (or any material for that matter), is the same methodology used for determining the L.H. of ice applicable? (e.g...